My invention pertains to locomotive speed control apparatus. More specifically, the invention relates to an improved automatic speed control for locomotives which provides greater accuracy and stability of the locomotive speed as the load handled by this locomotive varies.
Speed control apparatus for automatically controlling the speed of humping locomotives is known in the railroad art. However, the known systems have limitations in retaining stability within the system while maintaining the speed within a selected band. In these systems, regulation of speed within a given tolerance requires a corresponding gain of the velocity error. That is, the closer the tolerance desired, the greater the gain required. However, as this gain is increased, the possibility of instability becomes greater. In hump locomotive applications, the load being pushed varies over a large range. For example, it is not uncommon to start with a train weighing 10,000 tons. As the cars are dropped over the hump, the load continues to decrease until the last car which may weigh only 10 tons or so. Since the tractive capability of the locomotive is constant, it can be realized that the overall system gain continues to increase as cars are humped. Thus in one prior system, due to the increased gain as the consist becomes lighter, instability occurs typically with 10 or fewer cars so that it is necessary to operate the locomotive manually. Another problem or limitation is the high setting on the brake pressure switch necessary to allow the locomotive operator to hold the train on the hump until a throttle position is achieved which will move the train upgrade. This high pressure setting hinders later operation as it requires excessive brake application to shut off the throttle when necessary to exercise manual control. A speed control system which eliminates these and other limitations is thus extremely desirable.
Accordingly, an object of my invention is an improved automatic locomotive speed control system.
Another object of the invention is a speed control system for hump locomotives which provides good speed regulation and improved operating stability.
A further object of my invention is automatic locomotive speed control apparatus with improved regulation of selected speed and a higher degree of stability.
Yet another object of the invention is speed control apparatus for a hump locomotive in which the concept of processing the error signal is shifted, when the speed error is reduced below a predetermined percentage of the selected speed, to achieve a more accurate response while retaining stability.
Still another object of my invention is a locomotive speed control system which obtains a desired speed by controlling a master power source output on the locomotive and also the locomotive throttle position, in proportion to a selected ratio of a desired speed, with an operational shift from a first to a second type processing when the speed error is reduced below a predetermined percentage of the desired speed.
A further object of the invention is an arrangement for controlling speed of a locomotive in which the difference between the actual and selected speeds, modified by the acceleration signal, is used directly to control power and throttle of the locomotive when the difference exceeds a predetermined percentage of the desired velocity and in which the difference signal is processed through an integrator network to provide hybrid control of the voltage signal controlling the power and throttle when the difference is less than the predetermined percentage of the desired velocity, the acceleration signal being used as an advance indication of the achievement of the desired speed to eliminate overrun.
Other objects, features, and advantages of my invention will become apparent from the following description when taken in connection with the appended claims and accompanying drawings.